You might find it easiest to think of them all first as resources. The client is a resource for the children to think of another point of view, so when they are working on the commission they are minded to consider how the work will be seen by the client and make adjustments accordingly.

The email or letter are resources for introducing the client and the work ahead.

The phone call is a resource for making contact with the client.

I’m aware this doesn’t answer your question, but it helps me not to worry too much about the jargon!

More technically speaking, the way you introduce or represent the resources could be by the use of sign - symbolic, iconic or enactive. For example if you have a telephone in your office (within the fiction) then you can ‘sign’ it in a number of ways. You could use a play phone, or a real (deactivated) phone, or a drawing of a phone, or a model of a phone. Each of these would (within the imaginary world) ‘represent’ a real phone.

A ‘symbol’ of the phone is generally considered to be more abstract, perhaps a drawing of a phone box on a map or a graphic on a floor plan.

An ‘iconic image’ – is a drawing of the phone.

An ‘icon’ would be something like a model of the phone.

A ‘sign’ is more complex because Dorothy Heathcote uses the word sign in a number of different ways. In one sense, ‘to sign’ something, like a phone, is to use some form of imagery, either iconic or symbolic.
But she also uses ‘signing’ in the enactive form. That is, ‘to sign’ a phone by picking up an imaginary phone ‘as if’ it was real (not pretending, which would be ironic). If the sign works then everyone present will understand that the person in role is using a phone, even though the phone only exists in their imagination.

She also talks of ‘signing something up’, which is to use signs (iconic, symbolic or enactive) to clearly indicate to those involved what is being represented. For example, when you invented the email from the client you would have ‘signed it up’ to look authentic - typed on a computer (not handwritten), laid-out graphically to look like a proper email, with: ‘From’; ‘Subject’; ‘Date’; ‘To’ etc. and written in the correct formal (or informal) style depending on how you wanted it to sound.

All of these signs help the children to suspend their disbelieve and to agree to the fiction (so long as they know it is a fiction and are not so beguiled as to think the email is real. That wouldn’t be good!).

It is a very complex field, not helped because different experts use the words in different ways. As teachers I think it is best for us not to worry too much about the precise terminology, but just to keep thinking of lots of different ways to make the work more exciting, challenging and authentic for the children, both inside and outside the fiction.

Further - Let go of the terminology unless it helps you with planning or reflecting on your work. The idea is to engage children in inquiry about the world (including the curriculum) and to use drama to do this.

'Signs' can be classified as 'symbolic', 'iconic'. or 'enactive'. Symbolic signs use symbol systems -- languages -- e.g. the words (and any attachments or photos) in any email are all symbolic of more than the actual words or images themselves. Iconic signs represent something one-to-one -- e.g. a piece of paper held up with 'email' written on it stands in for an email. Enactive signs are anything that is moving and usually talking as if in the life of someone not actually present -- e.g. a video recording of someone emailing someone else.

In any use of 'drama' you are always creating an imagined-and-everyday space that you are hoping will 'grow' into an imagined-and-everyday world. Imagined spaces are always 'signed' by 'signs' that point to spaces that are not actually there e.g. the world of a book or the world of a group of experts. Because they are always lived through by you and the children they are always -everyday spaces as well as being imagined. You negotiate the use a signs with children in the everyday world of the classroom to open up imagined-and-everyday spaces. Children have to know what they are looking at -- they have to 'see' what the sign signifies and you have to negotiate that with them. 'When I sit down here I'm going to imagine that I'm writing an email. OK?' 'If you look at this piece of paper can we agree it represents an email?' 'Listen to me read this email. Who do you think wrote it? What do you think they want?'

Ask yourself - 'Where do you want to go in imagination with the children?' and 'How can you use signs to open up those imagined-and-everyday spaces?'

Try reflecting on what you do and how you use signs. You can consider other ways of doing the same thing if what you did worked/didn't 'work'.

If you think of 'signs' as 'texts' this may help you understand how to most effectively use them.

Texts are written/composed and read/interpreted. An enactive sign (you as if on a video or you as if you are another person actually talking with the children) is 'written' as you talk and move etc). An iconic sign is 'written' or composed when you draw it or choose it from a book. A symbolic sign is the language you are using -- the words themselves, the music you play, the formal gesture you use etc. The language has been written by others and you choose to use the language to communicate.

All texts are used to communicate. So an important question is, 'What do you want the children to "read" in your sign?' 'What do you want it to do for you and for them?'

This takes you to content and context. Why are you using drama in the first place? Where are you imagining you are?

Any sign you use is a text that has to be 'read' and interpreted. Icons always stand still. Photographs, drawings, maps etc. are relatively 'easy' to read because they don't move around.

Symbolic signs have to be decoded to make sense (we read the English language) we have to know the languages of maths or dance to know what is being said etc. So symbolic signs are often harder to read -- they assume readers already know a lot and they may be 'saying' more than you intended (in the language of an email, for example).

Enactive signs don't stand still either unless you 'freeze' them or slow them down. Reading a person's movements is hard because once it's 'enacted' it's over. But if you have a s sequence of photographs or a video of them you can read and reread that text and have the time to interpret it.

All of this happens in everyday life. Which often passes children without being examined. The wonder of the arts and especially of drama (and MoE as a system that uses drama) is that you can create your own texts and interpret them.

BUT if you don't know what you're inquiry is all about -- why you are doing the work -- then you won't know what you're trying to communicate and have the children think and reflect about.

So, as you try to make sense of signs go back to purposes. Ask yourself why you are using drama and then you can ask HOW can I use signs to assist me to do that.